The present invention relates to paper making machines and, more particularly, to a compact multilevel paper making machine for manufacturing a web of paper.
Generally, in a paper making machine, a wet paper web is formed in a former on a forming fabric and then moved downstream. Further, as the web is transported downstream in the paper making machine with a drying fabric, it is processed through a dewatering and/or a drying section where it is dewatered and/or dried, respectively. In some configurations of paper making machines, the forming fabric may also comprise the drying fabric. In alternate configurations of paper making machines, the drying fabric may be a separate fabric from the forming fabric, wherein the paper web is formed on the forming fabric and then transferred therefrom to the drying fabric for transportation through the dewatering and/or the drying section. Thus, references herein to a web-receiving region are intended to include the above-described configurations for the paper web being received by the drying fabric.
The drying section may include, for example, one or more of a through-air dryer (TAD), an infrared dryer, an impingement dryer, a cylindrical contact dryer, or the like. The paper making machine may further provide for additional drying of the web with another drying section comprising, for instance, a Yankee dryer. In this configuration, the web and fabric are passed downstream through a nip where the web is transferred to the Yankee dryer from the fabric. Generally, where a Yankee dryer follows the dryers in the upstream section, the dryers in the upstream section are regarded as pre-dryers for partially drying the paper web. These pre-dryers may further be regarded as comprising a part of the drying section or collectively forming a separate pre-drying section. Where the paper making machine includes a pre-drying section and a Yankee dryer, the Yankee dryer is accordingly regarded as the final dryer for drying the paper web. However, where the paper making machine does not include a Yankee dryer, the dryers in the upstream section comprise the final dryers for drying the paper web. Thus references herein to a drying section are intended to include either of the above configurations with regard to the definitions of a drying section and a pre-drying section. After final drying of the paper web, the web is directed to a reel-up where it is wound onto a spool to form a finished roll of paper.
As the paper web proceeds from the web-receiving region to the final dryer, the processes therebetween often leave residue from the paper web on the fabric or fabrics used to transport the paper web through the paper making machine. Thus, for proper operation of the paper making machine, the web-carrying fabrics are passed through a cleaning section before they return to the web-receiving region.
A paper making machine thus generally comprises one or more fabrics carrying a paper web, a drying section where the web is dried by one or more dryers, a cleaning section where the fabric is cleaned before returning to a web-receiving region, and a reel-up for receiving the dried paper web and winding it onto a spool. The paper making process is typically accomplished by having the pre-drying and/or drying section and the reel-up all disposed on essentially the same vertical level, with the web processing generally along a single direction from one end of the machine where it enters the pre-drying or drying section, to the other end where it is wound onto the roll in the reel-up. Where a Yankee dryer is used for final drying in a paper making machine, the rotations of the loop and the Yankee dryer (which is a rotatable drying cylinder) are coordinated such that the web is transferred to the Yankee dryer and carried over the top thereof in an upright orientation before being creped by the doctor blade. Creping the web in an upright orientation requires the web leaving the dewatering or the pre-drying section to encounter an upwardly moving surface of the Yankee dryer at the nip. Once dried by the Yankee dryer and creped, the dried web is transported to the reel-up to be wound onto a spool.
Prior art paper making machines exhibit some disadvantages resulting from the basic layout described. For example, in the typical configuration of a paper making machine, the machine occupies a large footprint because the web is transported from the web-receiving region, through the pre-drying section, onto the Yankee dryer, and to the reel-up, all in the same general direction and normally on a single floor or level. That is, the required machine hall length of a typical paper making machine is quite high. The high machine hall length poses a problem where the paper making machine must be installed in a building having the required amount of floor area, but where the floor area is divided among multiple levels or floors. Thus, the machine may not be able to fit on the designated level and the cost of modifying the existing building to accommodate the machine may be very expensive. In addition, if a new building was to be built to accommodate the machine, the large footprint of typical paper making machines would add significant cost to the building since the cost per linear foot of machine hall length is usually quite high. Thus, it is generally disadvantageous in terms of cost to have a paper making machine with a large footprint.
Another disadvantage of prior art paper making machines is that, where the cleaning section is disposed above the drying section, the paper web is usually transported from the web-receiving section to the nip in an inverted web run. The inverted web run does not allow the fabric to support the web and thus may lead to the possibility of the web falling off the fabric as it is being transported. In addition, elaborate catch pans and measures to prevent condensation must be implemented to prevent cleaning water from dripping from the cleaning section onto the underlying drying section in paper making processes involve special fabrics, such as TAD fabrics or other texturing fabrics used in tissue manufacturing which typically have an open structure and are more sensitive to water drip.
Thus, it would be desirable to provide a paper making machine configured such that the machine is compact and has a relatively small footprint in order to reduce the costs associated with housing the machine. In addition, it would be desirable to provide a paper making machine configured such that the paper web is transported on the fabric and through the drying section to the nip on an upper surface of the fabric, in order for the fabric to support the web and lessen the possibility of the web falling therefrom. Further, it would be desirable to provide a paper making machine configured such that the cleaning section is not located above the drying section, thus obviating the need for elaborate means for preventing the cleaning water from dripping from the cleaning section onto the underlying drying section.
The above and other needs are met by the present invention which, in one embodiment, provides a compact multilevel paper making machine comprising a web-receiving region where a web of paper is received on a fabric forming a continuous loop, a reel-up for winding the paper web onto a roll, and a web transfer point disposed between the web-receiving region and the reel-up. The fabric receives the web at the web-receiving region and then supports and transports the web from the web-receiving region to the web transfer point in a first direction on a first defined vertical level. At the web transfer point, the web is separated from the fabric. Following separation from the fabric, the web is transported to the reel-up in a second direction, generally opposite to the first direction, and on a second defined vertical level different from the first defined vertical level. The second defined vertical level may be either vertically above or below the first defined vertical level, wherein a defined vertical level may comprise, for instance, a floor of a building. Thus, by configuring the paper making machine to transport the web between different defined vertical levels, a compact multilevel paper making machine having a small footprint is provided for limited-space installations.
In accordance with certain embodiments of the present invention, the paper making machine may further comprise a dewatering section and/or a drying section, the drying section comprising at least one non-compacting dryer, disposed between the web-receiving region and the web transfer point such that the web-receiving region and the dewatering section and/or the drying section are disposed on the first defined vertical level.
In alternate embodiments of the paper making machine according to the present invention, the paper making machine may further comprise a drying section, the drying section including a Yankee dryer disposed between the web transfer point and the reel-up such that the Yankee dryer and the reel-up are disposed on the second defined vertical level.
Further alternate embodiments of the paper making machine according to the present invention may comprise a dewatering section and/or a pre-drying section, the pre-drying section comprising at least one non-compacting dryer, disposed between the web-receiving region and the web transfer point such that the web-receiving region and the dewatering section and/or the pre-drying section are disposed on the first defined vertical level, and a drying section, typically comprising a Yankee dryer, disposed between the web transfer point and the reel-up such that the Yankee dryer and the reel-up are disposed on the second defined vertical level.
It will further be appreciated that embodiments of the present invention which locate machine components on different defined vertical levels, with one of the defined vertical levels being disposed vertically over the other, provide multilevel layouts of a paper making machine, thereby reducing the footprint of the machine and resulting in a more compact installation thereof. The compact installation with reduced footprint of the machine thereby reduces the machine hall cost. It will be recognized, therefore, that the invention facilitates the achievement of a number of distinct advantages over prior art paper making devices.
Thus, it will be appreciated that embodiments of the present invention enable a wet paper web to be supported on an upper surface of a continuous fabric, wherein the web is carried on the fabric through dryers and/or other water-removing devices in such a way that the web will not fall off the fabric and such that the cleaning section is not located above any part of the web. Accordingly, there is no need for elaborate means for preventing the cleaning water from dripping from the cleaning section onto the web, as is necessary in prior art paper making processes employing a cleaning section above the drying section. The elimination of the possibility of cleaning water dripping onto the fabric and web is especially advantageous in paper making machines employing special texturing fabrics or through-air drying fabrics.